Interpretive Summary: Bacteriophage of Agrobacterium tumefaciens for control of walnut crown gall. C.G.EAYRE. USDA ARS, 9611 S. Riverbend Ave. Parlier, CA 93611.
Crown gall, caused by Agrobacterium tumefaciens, is a problem in many crops, particularly walnuts. There is no satisfactory control measure. The objective of this research was to test the disease control efficacy of bacteriophage of A. tumefaciens. Bacteriophage were isolated from soils by enrichment on nutrient broth with cultures of A. tumefaciens. Enrichments were purified by chloroform treatment, tested for ability to form plaques on bacterial lawns, and singly plaqued three times for homogeneity. Host range tests were performed, and two isolates selected for efficacy testing. Phage were increased by growth in the host on nutrient broth and purified by chloroform and PEG methods. Phage preparations were applied to roots of 2-year-old walnut trees in cold storage, and trees planted in three field trials. Treatments were two phage strains, a combination of the two strains, and a sterile buffer control. Each trial included 7 replications, and 10 trees per plot. After seven months roots were excavated and observed for galls. In two of the trials, one treatment had significantly fewer galls than the controls. Bacteriophage are a potential biological control for crown gall.

Technical Abstract:
Bacteriophage of <i>Agrobacterium tumefaciens<i> for control of walnut crown gall. C.G.EAYRE. USDA ARS, 9611 S. Riverbend Ave. Parlier, CA 93611.
Crown gall, caused by <i>Agrobacterium tumefaciens<i>, is a problem in many crops, particularly walnuts. There is no satisfactory control measure. The objective of this research was to test the disease control efficacy of bacteriophage of <i>A. tumefaciens<i>. Bacteriophage were isolated from soils by enrichment on nutrient broth with cultures of <i>A. tumefaciens<i>. Enrichments were purified by chloroform treatment, tested for ability to form plaques on bacterial lawns, and singly plaqued three times for homogeneity. Host range tests were performed, and two isolates selected for efficacy testing. Phage were increased by growth in the host on nutrient broth and purified by chloroform and PEG methods. Phage preparations were applied to roots of 2-year-old walnut trees in cold storage, and trees planted in three field trials. Treatments were two phage strains, a combination of the two strains, and a sterile buffer control. Each trial included 7 replications, and 10 trees per plot. After seven months roots were excavated and observed for galls. In two of the trials, one treatment had significantly fewer galls than the controls. Bacteriophage are a potential biological control for crown gall.